[dataflow]: PATCH COMMITTED

Andrew Pinski pinskia@gmail.com
Wed Nov 15 16:35:00 GMT 2006


On Wed, 2006-11-15 at 10:54 -0500, Kenneth Zadeck wrote:
> 
> The conversation was made on or right before sept 21.  Maybe danny can
> find the irc log.

I can remember part of the conversation.  The issue is that a plain
unspec without a set is always un-deletable instruction.

So:
(insn (unspec (xxxx) )

Should not be deleted even if it does not set anything.

In the ia64, it is used like use but use are useless after reload or at
least that is what the comment says:
;; As USE insns aren't meaningful after reload, this is used instead
;; to prevent deleting instructions setting registers for EH handling
(define_insn "prologue_use"
  [(unspec:DI [(match_operand:DI 0 "register_operand" "")]
              UNSPEC_PROLOGUE_USE)]


Thanks,
Andrew Pinski




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